A number of catalysts are known to be effective for the oxidation of acrolein, or methacrolein to acrylic acid or methacrylic acid, respectively. However, the yields obtained using the catalysts for the preparation of methacrylic acid are low. The present invention is a result of a search for more efficient and desirable catalysts for the production of acrylic acid and methacrylic acid. Unexpected higher yields of and selectivities to acrylic acid and methacrylic acid are obtained by the vapor phase oxidation of acrolein and methacrolein, respectively, with molecular oxygen in the presence of the new and useful catalysts of the present invention.
Belgian Pat. No. 828,074 teaches the use of a catalyst containing phosphorus, molybdenum, bismuth, copper, at least one of F, Ni, Co, and K, and optionally, Li, Na, Rb, Cs, Be, Mg, Ca, Sr, or Ba in the preparation of maleic anhydride.
French Pat. No. 1,601,955 teaches use of a catalyst in the preparation of maleic anhydride which has the composition AO.sub.3 --B.sub.2 O.sub.5 --M.sub.2 O.sub.5 --N.sub.x O--R.sub.2 O wherein A is Cr, Ag, Fe, Co or Ni; B is V or Nb; M is P, As, Sb or Bi; N is Cu, Ag, Fe, Co or Ni and R is Li, Na, K, Cs or Rb. Preferred composition is 15-55% atomic % A, 30-70% B, 0-15% M, 0.1-20% N, and 0-15% R.